Method and apparatus for writing optical recording media with optimum value of write power

Abstract

A method and apparatus for writing information on an optical recording medium by setting an optimum write power for recording information on the optical recording medium. First a series of test patterns is written on the medium, each test pattern being written with a different write power. On reading the test patterns, the modulation of each read signal is determined. The modulations as a function of write power are curve-fitted to an analytic function. The normalised derivative of this function is determined analytically and is used to determine the value of the optimum write power for the medium.

I claim: 
     
       1. A method for writing information on an optical recording medium by setting an optimum write power level of a radiation beam, comprising the following steps: writing a series of test patterns on the recording medium, each pattern with a different value of the write power level,   reading the patterns to form corresponding read signals,   deriving a value of a read parameter from each read signal,   curve-fitting the values of the read parameter to a function defining a relation between the write power level and the read parameter,   determining a derivative of the function and normalising the derivative by multiplying it by a factor equal to the value of the write power over the value of the read parameter, and   selecting the optimum write power level dependent upon the normalised derivative of the function.   
     
     
       2. A method for writing information on an optical recording medium by setting an optimum write power level of a radiation beam, comprising: writing a series of test patterns on the recording medium, each pattern with a different value of the write power level,   reading the patterns to form corresponding read signals,   deriving a value of a read parameter from each read signal,   curve-fitting the values of the read parameter to a function defining a relation between the write power level and the read parameter,   selecting the optimum write power level dependent upon a predetermined value of a derivative of the function normalised by multiplication by a factor equal to the value of the write power over the value of the read parameter.   
     
     
       3. The method according to claim 1, wherein the function is defined in terms of orthogonal polynomials. 
     
     
       4. The method according to claim 3, wherein the polynomials are Legendre polynomials. 
     
     
       5. The method according to claim 1, wherein the read a parameter is an amplitude of a read signal. 
     
     
       6. The method according to claim 1, wherein the selecting step includes reading a parameter value from the recording medium and using that value in selecting the value of the write power level. 
     
     
       7. The method according to claim 1, wherein the derivative of the function is determined analytically. 
     
     
       8. The method according to claim 1, wherein the selecting step includes selecting a power level dependent upon the derivative of the function and subsequently determining the optimum power level by multiplying the power level by a constant larger than one. 
     
     
       9. The method according to claim 2, wherein the selecting step includes selecting a power level dependent upon the derivative of the function and subsequently determining the optimum power level by multiplying the power level by a constant larger than one. 
     
     
       10. An apparatus for writing information on an optical recording medium, comprising: a radiation source for emitting a radiation beam having a controllable write power level, a control unit for writing a series of test patterns, each pattern with a different value of the write power level, a read unit for reading the patterns and forming corresponding read signals, a first processor for deriving a value of a read parameter from each read signal, a second processor for curve-fitting the values of the read parameter to a function defining a relation between the write power level and the read parameter, wherein the second processor includes means for deriving a derivative of the function, means for normalising the derivative by multiplying it by a factor equal to the value of the write power over the value of the read parameter, and means for selecting a value of the write power level dependent upon the normalised derivative of the function. 
     
     
       11. The apparatus according to claim 10, wherein the read parameter is an amplitude of a read signal. 
     
     
       12. The method according to claim 2, wherein the function is defined in terms of orthogonal polynomials. 
     
     
       13. The method according to calim 12, wherein the polynomials are Legendre polynomials. 
     
     
       14. The method according to claim 2, wherein the read parameter is an amplitude of a read signal. 
     
     
       15. The apparatus according to claim 10 wherein the function is defined in terms of orthogonal polynomials. 
     
     
       16. The apparatus according to claim 10 wherein the second processor further comprises means for reading a parameter value from the recording medium and using said value in selecting the value of the write power level. 
     
     
       17. The apparatus according to claim 10 wherein the second processor further comprises means for selecting a power level dependent upon the derivative of the function, and means for determining the optimum power level by multiplying the power level by a constant factor larger than 1.